Coupling is the significant characteristic of parallel mechanism,while it is just the coupling that brings about much difficulty for the configuration design,theoretical analysis and the development of the control sys...Coupling is the significant characteristic of parallel mechanism,while it is just the coupling that brings about much difficulty for the configuration design,theoretical analysis and the development of the control system of the parallel mechanism. And recently,the research on the decoupled parallel mechanism becomes one of the research hot points in the mechanism fields. In this paper,a type synthesis method for the translational decoupled parallel mechanism( TDPM) is proposed based on the screw theory. To achieve the decoupling characteristics of the translational parallel mechanism,the translational decoupled criterion for type synthesis of the branches are presented in this paper. According to this criterion and the realization conditions of rotational degree of freedom of the mechanism proposed former,a large number of branches for the TDPM are obtained. Taking the three degrees of freedom( DOFs) TDPM as an example,the process of type synthesis is discussed in detail. Using this proposed type synthesis method,a serial of translational decoupled parallel mechanisms, including but not limited to all the existing typical 3-DOF TDPMs, are obtained, which identifies the correctness and effective of the method. The contents of this paper provide a reference and possess significant theoretical meanings for the synthesis and development of the novel decoupled parallel mechanisms.展开更多
Objectives: To explore the treatment and related prognosis of elderly patients with Anderson II odontoid fracture with posterior pedicle screw fixation combined with iliac bone grafting. Methods: Retrospective analysi...Objectives: To explore the treatment and related prognosis of elderly patients with Anderson II odontoid fracture with posterior pedicle screw fixation combined with iliac bone grafting. Methods: Retrospective analysis of 17 cases of elderly patients with Anderson II odontoid fracture who underwent posterior pedicle screw fixation combined with iliac bone grafting from January 2013 to December 2016. 17 patients had a history of trauma before surgery, and they all have varying degrees of atlantoaxial instability or subluxation and varying degrees of neck occipital pain and limited mobility. Result: No spinal cord or vertebral artery injury occurred during surgery. Follow-up information is complete. The follow-up period was 6 to 48 months (mean 27.4 ± 12.4 months). Postoperative imaging review prompted a good reduction of cervical spine, stable sequence;no pedicle screw loosening, fracture, iliac bone graft at the location of the situation, odontoid fracture and bone healing at the good, the patient after cervical rotation are limited to varying degrees. Conclusion: Posterior pedicle screw fixation combined with iliac bone grafting in elderly patients with Anderson II odontoid fracture can achieve good stability, and the prognosis is good, but long-term cervical rotation function may be affected to varying degrees.展开更多
With the new pepper cultivar Guanlong as a test material, effects of differ-ent fertilizer application modes on growth and development, yield and photosynthetic characteristics of pepper were studied. The results show...With the new pepper cultivar Guanlong as a test material, effects of differ-ent fertilizer application modes on growth and development, yield and photosynthetic characteristics of pepper were studied. The results showed that the plant height and plant expansion of pepper in T4 were the largest, of 104.3 and 90.6 cm, respec-tively. T1 showed the largest weight of single fruit, fruit length and fruit diameter, re-spectively of 101.6 g, 25.49 cm and 4.86 cm. The content of total chlorophyl in the leaves of T1 was the highest, of 66.7 mg/g, and the root activity of T1 was also the highest, of 100.6 g/（g·FW·h）. The net photosynthetic rate of pepper leaves in T5 was the highest, of 6.6 μmol/（m^2·s）, while the net photosynthetic rates of T1 and T2 were the lowest, fluctuating in the range of 1.3-2.5 μmol/（m^2·s）. T3 showed the highest decrease amplitude of stomatal conductance in pepper leaves, of 2 658.1 mol/（m^2·s）, while the decrease amplitudes of stomatal conductance of pepper leaves in treatments T2 and T5 were the lowest, fluctuating in the range of 386.7-428.7 mol/（m^2·s）. T1 showed the highest decrease amplitude of transpiration rate of pepper leaves, of 4.7 mmol/（m^2·s）, while treatment T5 showed the lowest decrease ampli-tude of transpiration rate of pepper leaves, of 1.1 mmol/（m^2·s）. The intercel ular CO2 concentration was the highest in the leaves of T5, of 436.8 μmol/mol. T1 showed the highest plot output, yield per hectare and benefit, of 340.1 kg, 96 448.5 kg/hm^2 and 162 865.6 Yuan/hm^2, respectively, while T3 exhibited the lowest plot output, yield per hectare and benefit, of 260.8 kg, 74 338.5 kg/hm^2 and 124 888.5 Yuan/hm^2, respec-tively.展开更多
Space deployable antenna is the key equipment in realizing the communication and data transmission between the spacecraft and the earth.In order to enrich the configurations of deployable antennas,the type synthesis o...Space deployable antenna is the key equipment in realizing the communication and data transmission between the spacecraft and the earth.In order to enrich the configurations of deployable antennas,the type synthesis of deployable mechanisms for ring truss antenna is conducted in this study.First,the principle of the constraint-synthesis method based on screw theory is briefly described,the structure of the ring truss deployable antenna and its folding principle are analyzed,and the ring truss mechanism is divided into upper edges,lower edges and linkages.Then,based on the constraint-synthesis method,the type synthesis of the basic unit edges is carried out,a series of basic unit mechanisms are obtained from combining the basic unit edge mechanisms,and five mechanism units with fewer joints and simple structures are selected.Furthermore,simulation models of the five ring truss deployable mechanisms are built in Solidworks and Matlab software,and the deploying process is verified by the movement simulation.Finally,mechanism characteristics of the five mechanisms are analyzed and discussed,and a prototype is manufactured,verifying the analysis in this paper.This research provides a new way for the type synthesis of spatial deployable mechanisms,and the ring truss deployable mechanisms obtained in this study can be well applied in the field of aerospace.展开更多
Based on the screw theory and the driven-chain principle,a methodology of structural synthesis for fully-decoupled two-translational(2T) and two-rotational(2R) parallel mechanism is proposed by analyzing the character...Based on the screw theory and the driven-chain principle,a methodology of structural synthesis for fully-decoupled two-translational(2T) and two-rotational(2R) parallel mechanism is proposed by analyzing the characteristics of the input-output relations for fully-decoupled parallel mechanisms.Firstly,according to the desired kinematic characteristics of fully-decoupled parallel mechanisms,a method is proposed by virtue of screw theory to synthesize the desired forms for both the direct and the inverse Jacobian matrices.Secondly,according to the feature of the direct and the inverse Jacobian matrices,the effective screws,the actuated screws and the mobile un-actuated screws of each leg are established based on the reciprocal screw theory and all possible topology structures fulfilling the requirements are obtained.Finally,the desired fully-decoupled parallel mechanisms can be synthesized by using the structural synthesis rule and structural synthesis of fullydecoupled 2T2R parallel mechanisms can be obtained exploiting the abovementioned methodology.In particular,the direct Jacobian matrix of each synthesized fully-decoupled 2T2R parallel mechanism is a non-zero diagonal matrix throughout the entire workspace.Motors are mounted on each leg and each one of them actuates one degree-of-freedom(Do F) of the fully-decoupled parallel mechanism through a one-to-one velocity relation.展开更多
The current parallel ankle rehabilitation robot(ARR)suffers from the problem of difficult real-time alignment of the human-robot joint center of rotation,which may lead to secondary injuries to the patient.This study ...The current parallel ankle rehabilitation robot(ARR)suffers from the problem of difficult real-time alignment of the human-robot joint center of rotation,which may lead to secondary injuries to the patient.This study investigates type synthesis of a parallel self-alignment ankle rehabilitation robot(PSAARR)based on the kinematic characteristics of ankle joint rotation center drift from the perspective of introducing"suitable passive degrees of freedom(DOF)"with a suitable number and form.First,the self-alignment principle of parallel ARR was proposed by deriving conditions for transforming a human-robot closed chain(HRCC)formed by an ARR and human body into a kinematic suitable constrained system and introducing conditions of"decoupled"and"less limb".Second,the relationship between the self-alignment principle and actuation wrenches(twists)of PSAARR was analyzed with the velocity Jacobian matrix as a"bridge".Subsequently,the type synthesis conditions of PSAARR were proposed.Third,a PSAARR synthesis method was proposed based on the screw theory and type of PSAARR synthesis conducted.Finally,an HRCC kinematic model was established to verify the self-alignment capability of the PSAARR.In this study,93 types of PSAARR limb structures were synthesized and the self-alignment capability of a human-robot joint axis was verified through kinematic analysis,which provides a theoretical basis for the design of such an ARR.展开更多
To avoid the existence of nonlinear and strong coupling in parallel mechanisms,it is necessary to address special care to the type synthesis of mechanisms,especially for the type synthesis of fully-decoupled parallel ...To avoid the existence of nonlinear and strong coupling in parallel mechanisms,it is necessary to address special care to the type synthesis of mechanisms,especially for the type synthesis of fully-decoupled parallel mechanisms. Based on the screw theory and the driven-chain principle,a methodology of structural synthesis for fully-decoupled three-rotational( 3R) and two-translational( 2T)parallel mechanisms was proposed by analyzing the characteristics of the input-output relations for fully-decoupled parallel mechanisms.Firstly,according to the desired kinematic characteristics of fullydecoupled parallel mechanisms,a method was presented by virtue of screw theory to synthesize the desired forms for both the direct and the inverse Jacobian matrices. Secondly,according to the feature of the direct and the inverse Jacobian matrices,the effective screws,the actuated screws and the mobile un-actuated screws of each leg were established based on the reciprocal screw theory and all possible topology structures fulfilling the requirements were obtained.Finally,the desired fully-decoupled parallel mechanisms could be synthesized by using the structural synthesis rule and structural synthesis of fully-decoupled 3R2 T parallel mechanisms could be obtained exploiting the abovementioned methodology. Furthermore,the Jacobian matrix of a synthesized 3R2 T parallel mechanism was deduced to demonstrate the decoupling feature of the parallel mechanism,which also validated the correctness of the methodology of the type synthesis for fully-decoupled 3R2 T parallel mechanisms.展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant No.51005195,51205339)
文摘Coupling is the significant characteristic of parallel mechanism,while it is just the coupling that brings about much difficulty for the configuration design,theoretical analysis and the development of the control system of the parallel mechanism. And recently,the research on the decoupled parallel mechanism becomes one of the research hot points in the mechanism fields. In this paper,a type synthesis method for the translational decoupled parallel mechanism( TDPM) is proposed based on the screw theory. To achieve the decoupling characteristics of the translational parallel mechanism,the translational decoupled criterion for type synthesis of the branches are presented in this paper. According to this criterion and the realization conditions of rotational degree of freedom of the mechanism proposed former,a large number of branches for the TDPM are obtained. Taking the three degrees of freedom( DOFs) TDPM as an example,the process of type synthesis is discussed in detail. Using this proposed type synthesis method,a serial of translational decoupled parallel mechanisms, including but not limited to all the existing typical 3-DOF TDPMs, are obtained, which identifies the correctness and effective of the method. The contents of this paper provide a reference and possess significant theoretical meanings for the synthesis and development of the novel decoupled parallel mechanisms.
文摘Objectives: To explore the treatment and related prognosis of elderly patients with Anderson II odontoid fracture with posterior pedicle screw fixation combined with iliac bone grafting. Methods: Retrospective analysis of 17 cases of elderly patients with Anderson II odontoid fracture who underwent posterior pedicle screw fixation combined with iliac bone grafting from January 2013 to December 2016. 17 patients had a history of trauma before surgery, and they all have varying degrees of atlantoaxial instability or subluxation and varying degrees of neck occipital pain and limited mobility. Result: No spinal cord or vertebral artery injury occurred during surgery. Follow-up information is complete. The follow-up period was 6 to 48 months (mean 27.4 ± 12.4 months). Postoperative imaging review prompted a good reduction of cervical spine, stable sequence;no pedicle screw loosening, fracture, iliac bone graft at the location of the situation, odontoid fracture and bone healing at the good, the patient after cervical rotation are limited to varying degrees. Conclusion: Posterior pedicle screw fixation combined with iliac bone grafting in elderly patients with Anderson II odontoid fracture can achieve good stability, and the prognosis is good, but long-term cervical rotation function may be affected to varying degrees.
基金Supported by National Staple Vegetables(CARS-25-G-50)~~
文摘With the new pepper cultivar Guanlong as a test material, effects of differ-ent fertilizer application modes on growth and development, yield and photosynthetic characteristics of pepper were studied. The results showed that the plant height and plant expansion of pepper in T4 were the largest, of 104.3 and 90.6 cm, respec-tively. T1 showed the largest weight of single fruit, fruit length and fruit diameter, re-spectively of 101.6 g, 25.49 cm and 4.86 cm. The content of total chlorophyl in the leaves of T1 was the highest, of 66.7 mg/g, and the root activity of T1 was also the highest, of 100.6 g/（g·FW·h）. The net photosynthetic rate of pepper leaves in T5 was the highest, of 6.6 μmol/（m^2·s）, while the net photosynthetic rates of T1 and T2 were the lowest, fluctuating in the range of 1.3-2.5 μmol/（m^2·s）. T3 showed the highest decrease amplitude of stomatal conductance in pepper leaves, of 2 658.1 mol/（m^2·s）, while the decrease amplitudes of stomatal conductance of pepper leaves in treatments T2 and T5 were the lowest, fluctuating in the range of 386.7-428.7 mol/（m^2·s）. T1 showed the highest decrease amplitude of transpiration rate of pepper leaves, of 4.7 mmol/（m^2·s）, while treatment T5 showed the lowest decrease ampli-tude of transpiration rate of pepper leaves, of 1.1 mmol/（m^2·s）. The intercel ular CO2 concentration was the highest in the leaves of T5, of 436.8 μmol/mol. T1 showed the highest plot output, yield per hectare and benefit, of 340.1 kg, 96 448.5 kg/hm^2 and 162 865.6 Yuan/hm^2, respectively, while T3 exhibited the lowest plot output, yield per hectare and benefit, of 260.8 kg, 74 338.5 kg/hm^2 and 124 888.5 Yuan/hm^2, respec-tively.
基金co-supported by the National Natural Science Foundation of China(No.51675458)the Key Project of Natural Science Foundation of Hebei Province of China(No.E201720335)the Youth Top Talent Project of Hebei Province Higher Education of China(No.BJ2017060)。
文摘Space deployable antenna is the key equipment in realizing the communication and data transmission between the spacecraft and the earth.In order to enrich the configurations of deployable antennas,the type synthesis of deployable mechanisms for ring truss antenna is conducted in this study.First,the principle of the constraint-synthesis method based on screw theory is briefly described,the structure of the ring truss deployable antenna and its folding principle are analyzed,and the ring truss mechanism is divided into upper edges,lower edges and linkages.Then,based on the constraint-synthesis method,the type synthesis of the basic unit edges is carried out,a series of basic unit mechanisms are obtained from combining the basic unit edge mechanisms,and five mechanism units with fewer joints and simple structures are selected.Furthermore,simulation models of the five ring truss deployable mechanisms are built in Solidworks and Matlab software,and the deploying process is verified by the movement simulation.Finally,mechanism characteristics of the five mechanisms are analyzed and discussed,and a prototype is manufactured,verifying the analysis in this paper.This research provides a new way for the type synthesis of spatial deployable mechanisms,and the ring truss deployable mechanisms obtained in this study can be well applied in the field of aerospace.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50905075)the Open Project of the State Key Laboratory of Robotics and System(Grant No.SKLRS-2016-KF-06)+2 种基金the Open Project of the State Key Laboratory of Mechanical System and Vibration of China(Grant No.MSV201407)the Open Project of Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology(Grant No.FM-201402)the Research and the Innovation Project for College Graduates of Jiangsu Province(Grant No.SJZZ16-0212)
文摘Based on the screw theory and the driven-chain principle,a methodology of structural synthesis for fully-decoupled two-translational(2T) and two-rotational(2R) parallel mechanism is proposed by analyzing the characteristics of the input-output relations for fully-decoupled parallel mechanisms.Firstly,according to the desired kinematic characteristics of fully-decoupled parallel mechanisms,a method is proposed by virtue of screw theory to synthesize the desired forms for both the direct and the inverse Jacobian matrices.Secondly,according to the feature of the direct and the inverse Jacobian matrices,the effective screws,the actuated screws and the mobile un-actuated screws of each leg are established based on the reciprocal screw theory and all possible topology structures fulfilling the requirements are obtained.Finally,the desired fully-decoupled parallel mechanisms can be synthesized by using the structural synthesis rule and structural synthesis of fullydecoupled 2T2R parallel mechanisms can be obtained exploiting the abovementioned methodology.In particular,the direct Jacobian matrix of each synthesized fully-decoupled 2T2R parallel mechanism is a non-zero diagonal matrix throughout the entire workspace.Motors are mounted on each leg and each one of them actuates one degree-of-freedom(Do F) of the fully-decoupled parallel mechanism through a one-to-one velocity relation.
基金Supported by Key Scientific Research Platforms and Projects of Guangdong Regular Institutions of Higher Education of China(Grant No.2022KCXTD033)Guangdong Provincial Natural Science Foundation of China(Grant No.2023A1515012103)+1 种基金Guangdong Provincial Scientific Research Capacity Improvement Project of Key Developing Disciplines of China(Grant No.2021ZDJS084)National Natural Science Foundation of China(Grant No.52105009).
文摘The current parallel ankle rehabilitation robot(ARR)suffers from the problem of difficult real-time alignment of the human-robot joint center of rotation,which may lead to secondary injuries to the patient.This study investigates type synthesis of a parallel self-alignment ankle rehabilitation robot(PSAARR)based on the kinematic characteristics of ankle joint rotation center drift from the perspective of introducing"suitable passive degrees of freedom(DOF)"with a suitable number and form.First,the self-alignment principle of parallel ARR was proposed by deriving conditions for transforming a human-robot closed chain(HRCC)formed by an ARR and human body into a kinematic suitable constrained system and introducing conditions of"decoupled"and"less limb".Second,the relationship between the self-alignment principle and actuation wrenches(twists)of PSAARR was analyzed with the velocity Jacobian matrix as a"bridge".Subsequently,the type synthesis conditions of PSAARR were proposed.Third,a PSAARR synthesis method was proposed based on the screw theory and type of PSAARR synthesis conducted.Finally,an HRCC kinematic model was established to verify the self-alignment capability of the PSAARR.In this study,93 types of PSAARR limb structures were synthesized and the self-alignment capability of a human-robot joint axis was verified through kinematic analysis,which provides a theoretical basis for the design of such an ARR.
基金National Natural Science Foundation of China(No.50905075)the Six Talent Peaks Project in Jiangsu Province,China(No.ZBZZ-012)+4 种基金the Fundamental Research Funds for the Central Universities,China(No.JUSRP51316B)the Open Project of the State Key Laboratory of Mechanical System and Vibration of China(No.MSV201407)the Open Project of the Key Laboratory of System Control and Information Processing,China(No.Scip201506)the Open Project of Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology,China(No.FM-201402)the Research and the Innovation Project for College Graduates of Jiangsu Province,China(No.KYLX-1115)
文摘To avoid the existence of nonlinear and strong coupling in parallel mechanisms,it is necessary to address special care to the type synthesis of mechanisms,especially for the type synthesis of fully-decoupled parallel mechanisms. Based on the screw theory and the driven-chain principle,a methodology of structural synthesis for fully-decoupled three-rotational( 3R) and two-translational( 2T)parallel mechanisms was proposed by analyzing the characteristics of the input-output relations for fully-decoupled parallel mechanisms.Firstly,according to the desired kinematic characteristics of fullydecoupled parallel mechanisms,a method was presented by virtue of screw theory to synthesize the desired forms for both the direct and the inverse Jacobian matrices. Secondly,according to the feature of the direct and the inverse Jacobian matrices,the effective screws,the actuated screws and the mobile un-actuated screws of each leg were established based on the reciprocal screw theory and all possible topology structures fulfilling the requirements were obtained.Finally,the desired fully-decoupled parallel mechanisms could be synthesized by using the structural synthesis rule and structural synthesis of fully-decoupled 3R2 T parallel mechanisms could be obtained exploiting the abovementioned methodology. Furthermore,the Jacobian matrix of a synthesized 3R2 T parallel mechanism was deduced to demonstrate the decoupling feature of the parallel mechanism,which also validated the correctness of the methodology of the type synthesis for fully-decoupled 3R2 T parallel mechanisms.
